Inkjet printheads are often supplied as a portion of an inkjet cartridge, which may be replaced when empty or beyond its service life. In a thermal fluid ejection system, a barrier layer containing ink channels and vaporization or firing chambers is located between a nozzle orifice plate and a substrate layer.
The substrate layer typically contains linear arrays of heater elements, such as firing resistors, which are energized to heat ink within the vaporization chambers. Upon heating, an ink droplet is ejected from a nozzle associated with the energized resistor. By selectively energizing the resistors as the printhead is moved across a page, ink is expelled in a pattern on the print media to form a desired image.
Careful regulation of the printhead temperature aids inkjet printing mechanisms in providing optimal print quality and reliability, while also extending printhead life. One method of monitoring printhead temperature uses a temperature sensing resister (“TSR”), which is embedded into the printhead during manufacture of the firing resistors.
However, in order to calibrate a printhead's TSR, an inkjet printer typically uses a separate ambient temperature sensor, which adds expense to the product and requires a complex calibration routine. This calibration system typically requires the printhead temperature to be brought to ambient temperature before start of a calibration routine, often requiring printers to be idle for nearly an hour before calibration. Furthermore, if a customer installs a new printhead and immediately begins printing with performing calibration, poor print quality or a shortening of the life of the printhead may result. For these and other reasons, there is a need for the present invention.